Nuclear Theory·nucl-th

Wednesday·December 20, 2017

8 papers—3 primary·5 cross-listed

01
[Submitted on 19 Dec 2017]
New Gogny interaction suitable for astrophysical applications
C. Gonzalez-Boquera · M. Centelles · X. Viñas · L. M. Robledo
The D1 family of parametrizations of the Gogny interaction commonly suffers from a rather soft neutron matter equation of state that leads to maximal masses of neutron stars well below the observational value of two solar masses. We propose a reparametrization scheme that preserves the good properties of the Gogny force but allows one to tune the density dependence of the symmetry energy, which, in turn, modifies the predictions for the maximum stellar mass. The scheme works well for D1M, and leads to a new parameter set, dubbed D1M*. In the neutron-star domain, D1M* predicts a maximal mass of two solar masses and global properties of the star in harmony with those obtained with the SLy4 Skyrme interaction. By means of a set of selected calculations in finite nuclei, we check that D1M* performs comparably well to D1M in several aspects of nuclear structure in nuclei.
Comments:
6 pages, 5 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE)
arXiv:
1712.06735 [pdf]
PLB(2018)·72 citations
02
[Submitted on 19 Dec 2017]
Exotic atoms at extremely high magnetic fields: the case of neutron star atmosphere
Andrea Fontana · Alessandro Colombi · Pietro Carretta · Alessandro Drago · Paolo Esposito · Paola Gianotti · Carlotta Giusti · Diego Lonardoni · Alessandro Lovato · Vincenzo Lucherini · Francesco Pederiva
The presence of exotic states of matter in neutron stars (NSs) is currently an open issue in physics. The appearance of muons, kaons, hyperons, and other exotic particles in the inner regions of the NS, favored by energetic considerations, is considered to be an effective mechanism to soften the equation of state (EoS). In the so-called two-families scenario, the softening of the EoS allows for NSs characterized by very small radii, which become unstable and convert into a quark stars (QSs). In the process of conversion of a NS into a QS material can be ablated by neutrinos from the surface of the star. Not only neutron-rich nuclei, but also more exotic material, such as hypernuclei or deconfined quarks, could be ejected into the atmosphere. In the NS atmosphere, atoms like H, He, and C should exist, and attempts to model the NS thermal emission taking into account their presence, with spectra modified by the extreme magnetic fields, have been done. However, exotic atoms, like muonic hydrogen $(p μ^{-})$ or the so-called Sigmium $(Σ^{+} e^{-})$ , could also be present during the conversion process or in its immediate aftermath. At present, analytical expressions of the wave functions and eigenvalues for these atoms have been calculated only for H. In this work, we extend the existing solutions and parametrizations to the exotic atoms $(p μ^{-})$ and $(Σ^{+} e^{-})$ , making some predictions on possible transitions. Their detection in the spectra of NS would provide experimental evidence for the existence of hyperons in the interior of these stars.
Comments:
10 pages, 6 figures, proceedings of the "International Conference on Exotic Atoms and Related Topics - EXA2017", Austrian Academy of Sciences, Austria, September 11-15, 2017
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); Atomic Physics (physics.atom-ph)
arXiv:
1712.06818 [pdf]
EPJ Web Conf.(2018)·0 citations
03
[Submitted on 19 Dec 2017]
Effects of chiral three-nucleon forces on $^{4}$ He-nucleus scattering in a wide range of incident energies
Masakazu Toyokawa · Masanobu Yahiro · Takuma Matsumoto · Michio Kohno
It is a current important subject to clarify properties of chiral three-nucleon forces (3NFs) not only in nuclear matter but also in scattering between finite-size nuclei. Particularly for the elastic scattering, this study has just started and the properties are not understood in a wide range of incident energies ( $E_{in}$ ). We investigate basic properties of chiral 3NFs in nuclear matter with positive energies by using the Brueckner-Hartree-Fock method with chiral two-nucleon forces of N $^{3}$ LO and 3NFs of NNLO, and analyze effects of chiral 3NFs on $^{4}$ He elastic scattering from targets $^{208}$ Pb, $^{58}$ Ni and $^{40}$ Ca over a wide range of $30 ≲ E_{in} / A_{P} ≲ 200$ MeV by using the $g$ -matrix folding model, where $A_{P}$ is the mass number of projectile. In symmetric nuclear matter with positive energies, chiral 3NFs make the single-particle potential less attractive and more absorptive. The effects mainly come from the Fujita-Miyazawa 2 $π$ -exchange 3NF and slightly become larger as $E_{in}$ increases. These effects persist in the optical potentials of $^{4}$ He scattering. As for the differential cross sections of $^{4}$ He scattering, chiral-3NF effects are large in $E_{in} / A_{P} ≳ 60$ MeV and improve the agreement of the theoretical results with the measured ones. Particularly in $E_{in} / A_{P} ≳ 100$ MeV, the folding model reproduces measured differential cross sections pretty well. Cutoff ( $Λ$ ) dependence is investigated for both nuclear matter and $^{4}$ He scattering by considering two cases of $Λ = 450$ and $550$ MeV. The uncertainty coming from the dependence is smaller than chiral-3NF effects even at $E_{in} / A_{P} = 175$ MeV.
Comments:
14 pages, 15 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1712.07033 [pdf]
PTEP(2018)·27 citations
04
[Submitted on 18 Dec 2017] (cross-list from hep-ph)
A no-go theorem for non-standard explanations of the $τ \to K_{S} π ν_{τ}$ CP asymmetry
Vincenzo Cirigliano🇺🇸 · Andreas Crivellin🇨🇭 · Martin Hoferichter🇺🇸
The CP asymmetry in $τ \to K_{S} π ν_{τ}$ , as measured by the BaBar collaboration, differs from the Standard Model prediction by $2.8 σ$ . Most non-standard interactions do not allow for the required strong phase needed to produce a non-vanishing CP asymmetry, leaving only new tensor interactions as a possible mechanism. We demonstrate that, contrary to previous assumptions in the literature, the crucial interference between vector and tensor phases is suppressed by at least two orders of magnitude due to Watson's final-state-interaction theorem. Furthermore, we find that the strength of the relevant CP-violating tensor interaction is strongly constrained by bounds from the neutron electric dipole moment and $D$ - $D ˉ$ mixing. These observations together imply that it is extremely difficult to explain the current $τ \to K_{S} π ν_{τ}$ measurement in terms of physics beyond the Standard Model originating in the ultraviolet.
Comments:
6 pages, 4 figures; version to be published in PRL
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
1712.06595 [pdf]
PRL(2018)·80 citations
05
[Submitted on 19 Dec 2017] (cross-list from hep-ph)
Electromagnetic field effects on $Υ$ -meson dissociation in PbPb collisions at LHC energies
J. Hoelck🇩🇪 · G. Wolschin🇩🇪
We investigate the effect of the electromagnetic field generated in relativistic heavy-ion collisions on the dissociation of $Υ$ mesons. The electromagnetic field is calculated using a simple model which characterizes the emerging quark-gluon plasma (QGP) by its conductivity only. A numerical estimate of the field strength experienced by $Υ$ mesons embedded in the expanding QGP and its consequences on the $Υ$ dissociation is made. The electromagnetic field effects prove to be negligible compared to the established strong-interaction suppression mechanisms.
Comments:
7 pages, 4 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1712.06871 [pdf]
EPJA(2017)·18 citations
06
[Submitted on 19 Dec 2017] (cross-list from hep-ph)
Fast neutrino flavor conversion: roles of dense matter and spectrum crossing
Sajad Abbar🇺🇸 · Huaiyu Duan (UNM)🇺🇸
The flavor conversion of a neutrino usually occurs at densities $≲ G_{F}^{- 1} ω$ , whether in the ordinary matter or the neutrino medium, and on time/distance scales of order $ω^{- 1}$ , where $G_{F}$ is the Fermi weak coupling constant and $ω$ is the vacuum oscillation frequency of the neutrino. In 2005 Sawyer and more recently both he and other groups have shown that neutrino flavor conversions can occur on scales much shorter than $ω^{- 1}$ in a very dense, anisotropic neutrino gas such as that in a core-collapse supernova or a binary neutron star merger. It has also been suggested that the fast neutrino flavor conversion require a crossing in the electron lepton number (ELN) angular distribution or spectrum. We study a few simple analytical models with which we elucidate the roles of the dense matter and the ELN spectrum crossing in neutrino fast flavor conversions. We show that a large matter density can induce fast neutrino flavor conversions in certain astrophysical scenarios such as at the early epoch of a core-collapse supernova.
Comments:
11 pages, 4 figures. Updated with editorial changes and clarifications
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
arXiv:
1712.07013 [pdf]
PRD(2018)·93 citations
07
[Submitted on 19 Dec 2017] (cross-list from hep-ph)
Gluon Shadowing in Heavy-Flavor Production at the LHC
Aleksander Kusina🇵🇱 · Jean-Philippe Lansberg🇫🇷 · Ingo Schienbein🇫🇷 · Hua-Sheng Shao🇫🇷
We study the relevance of experimental data on heavy-flavor [ $D^{0}$ , $J / ψ$ , $B \to J / ψ$ and $Υ (1 S)$ mesons] production in proton-lead collisions at the LHC to improve our knowledge of the gluon-momentum distribution inside heavy nuclei. We observe that the nuclear effects encoded in both most recent global fits of nuclear parton densities at next-to-leading order (nCTEQ15 and EPPS16) provide a good overall description of the LHC data. We interpret this as a hint that these are the dominant ones. In turn, we perform a Bayesian-reweighting analysis for each particle data sample which shows that each of the existing heavy-quark(onium) data set clearly points --with a minimal statistical significance of 7 $σ$ -- to a shadowed gluon distribution at small $x$ in the lead. Moreover, our analysis corroborates the existence of gluon antishadowing. Overall, the inclusion of such heavy-flavor data in a global fit would significantly reduce the uncertainty on the gluon density down to $x ≃ 7 \times 1 0^{- 6}$ --where no other data exist-- while keeping an agreement with the other data of the global fits. Our study accounts for the factorization-scale uncertainties which dominate for the charm(onium) sector.
Comments:
4 pages + references + appendix, 1 figure; v2: match to the journal version, add the supplemental material
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1712.07024 [pdf]
PRL(2018)·170 citations
08
[Submitted on 19 Dec 2017] (cross-list from hep-ph)
Illuminating the photon content of the proton within a global PDF analysis
Valerio Bertone🇳🇱 · Stefano Carrazza🇨🇭 · Nathan P. Hartland🇳🇱 · Juan Rojo🇳🇱
Precision phenomenology at the LHC requires accounting for both higher-order QCD and electroweak corrections as well as for photon-initiated subprocesses. Building upon the recent NNPDF3.1 fit, in this work the photon content of the proton is determined within a global analysis supplemented by the LUXqed constraint relating the photon PDF to lepton-proton scattering structure functions: NNPDF3.1luxQED. The uncertainties on the resulting photon PDF are at the level of a few percent, with photons carrying up to 0.5% of the proton's momentum. We study the phenomenological implications of NNPDF3.1luxQED at the LHC for Drell-Yan, vector boson pair, top quark pair, and Higgs plus vector boson production. We find that photon-initiated contributions can be significant for many processes, leading to corrections of up to 20%. Our results represent a state-of-the-art determination of the partonic structure of the proton including its photon component.
Comments:
29 pages, 19 figures, minor corrections
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
1712.07053 [pdf]
SciPost Phys.(2018)·292 citations

Affiliations

first authorsco-authorsvia INSPIRE